The present invention relates to an ultrasound diagnostic apparatus which is suitable for measuring an elastic modulus of a vascular wall, and in particular, to an ultrasound diagnostic apparatus which can automatically detect a blood vessel anterior wall boundary from a B-mode image.
An ultrasound diagnostic apparatus using an ultrasound image has hitherto been put into practical use in the field of medicine.
In general, this type of ultrasound diagnostic apparatus has an ultrasound probe (hereinafter, referred to as a probe) and a diagnostic apparatus body. Ultrasonic waves are transmitted from the probe toward a subject, an ultrasonic echo from the subject is received by the probe, and a reception signal is electrically processed by the diagnostic apparatus body to produce an ultrasound image.
Ultrasonic waves are transmitted toward a blood vessel, a cardiac wall, or the like, an ultrasonic echo therefrom is received, and a reception signal is analyzed to obtain the displacement of a vascular wall or the like. The elastic modulus of the vascular wall, the cardiac wall (heart muscle), or the like is measured from the displacement.
For example, JP 10-5226 A describes a technique in which ultrasonic waves are transmitted and received with respect to an object moving in synchronization with the heartbeats (cardiac pulsation) to obtain a reception signal of an ultrasonic echo, the instantaneous position of the object is determined using the amplitude and phase of the reception signal, and the large-amplitude displacement motion of the vascular wall based on the heartbeats is tracked, thereby obtaining the elastic modulus of the blood vessel.
Specifically, the motion velocity waveform of minute vibration of the vascular wall is obtained on the basis of the sequential position of the vascular wall, the tracking trajectory of each of the sections at a predetermined interval in the depth direction in the vascular wall is obtained, and a temporal change in thickness of each section is calculated to obtain the elastic modulus of the blood vessel.
Similarly, JP 2010-233956 A describes an ultrasound diagnostic apparatus which obtains the displacement of a blood vessel or the like from a reception signal of an ultrasonic echo obtained when ultrasonic waves are transmitted and received with respect to an object moving in synchronization with the heartbeats, and obtains an elastic modulus from the displacement.
In this ultrasound diagnostic apparatus, a B-mode image and an M-mode image are produced using a reception signal obtained from an object, such as a blood vessel. Blurring due to hand or body movement is detected from the reception signal of the M-mode image, and the positional variation of the probe and the subject is detected using the reception signal of the M-mode image where the blurring is detected. The accuracy of the reception signal is determined from the detection result, and the displacement of the object is obtained using the reception signal of the M-mode image whose accuracy is determined to be high, and the elastic modulus of the vascular wall or the like is measured from the displacement.
Such measurement of the blood vessel elastic modulus or the like in an ultrasound diagnostic apparatus is normally performed by selecting the position in the azimuth direction on the B-mode image, at which the M-mode image is displayed, using a display line (line of interest) or the like, displaying and analyzing the M-mode image of the selected display line, and detecting the shift or moving velocity of the vascular wall.
As described in JP 2010-233956 A, in the ultrasound diagnostic apparatus, the anterior wall of the blood vessel is detected with difficulty compared to the posterior wall (deep side) of the blood vessel. For this reason, in many cases, the analysis is performed using the blood vessel posterior wall.